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UDK - More lighting shadow problems UV Help/Plz

tulkas09
polycounter lvl 7
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tulkas09 polycounter lvl 7
Hey i just tried to follow a lot of tutorials and instrucctions but i cant solve this problem:

I create a wall with 2 windows, low poly 200 tris the wall with the windows. And let me show you the problems...

static mesh properties:
dwm2013011121325002.jpg

Un the static mesh actor i already try with on/off ovveride and shadow indirect...

world properties:
dwm2013011121334139.jpg

Here i only have change the light masss bounces

mesh properties:
dwm2013011121352114.jpg

And here you are watching the second uw for the shadows, in UV channel 0 is the diffuse one...

healp!! :(
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Replies

  • ZacD
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    ZacD ngon master
    1 sided meshes do not cast shadows properly, either add a roof, or make the existing models solid.
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  • r4ptur3
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    r4ptur3 polycounter lvl 17
    Go to the properties of your placed objects (f4) and search for "cast shadow as two sided". Light will pass through meshes with open faces -- the shadows are technically correct if you look at the wall from the back side.
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  • ZacD
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    ZacD ngon master
    Isn't it more expensive to use cast shadow as two sided than to just making it a solid mesh?
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  • tulkas09
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    tulkas09 polycounter lvl 7
    With the double-sided shadows it works so much better, and now I have the same question too, its cheaper with this double-sided shadows or making the object with 2 sides?

    Thanks :D
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  • ZacD
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    ZacD ngon master
    It's bad practice, not all engines can do it, and it's often better to manual duplicate and invert faces because you do not need everything double sided. I'm not sure if it adds another draw call, or causes any direct performance hit, I'd have to test it out. But two sided shader turns off backface culling and forces the GPU to render all triangles twice.
    perna wrote: »
    oh, btw a huge myth is about backface culling (double sided rendering) and how people think that it's somehow more efficient than simply duplicating the polygons. It isn't. In most cases it's a terrible solution... most people just like it because it maintains and artificially low tricount for their asset. Not gonna go in depth on this one for now, someone else may want to.
    CrazyButcher wrote: »
    To disable backface culling for the entire thing if only a few polys need to be duplicated is wasteful. The majority of backfaces of thee object, that don't need this would hurt performance. For "batching" it would also be bad to mix objects that require this to be turned off and others not. However if you have a lot of stuff that requires it off, and all can be combined (think lots of window planes) then there is no need to duplicate manually as the hw rasterizer does it for free.

    http://www.polycount.com/forum/showpost.php?p=1211374&postcount=91
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  • r4ptur3
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    r4ptur3 polycounter lvl 17
    Yeah, I am pretty sure UDK has to draw the back faces of every poly in the mesh. It's way cheaper to just but two tris back there and close up the mesh.
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